ACAR (Aluminum Conductor Alloy Reinforced) — Complete Technical Specification & Selection Guide
ACAR (Aluminum Conductor Alloy Reinforced) — Complete Technical Specification & Selection Guide
Aluminum Conductor Alloy Reinforced (ACAR) is a high-performance overhead transmission conductor that uses high-strength aluminum alloy wires as the reinforcing core, with electrical conductor (EC) grade aluminum wires stranded concentrically around it. ACAR combines the high conductivity of aluminum with the superior strength of aluminum alloy, offering exceptional engineering value for long-distance transmission, long-span crossings, and heavy ice zones. This article provides a systematic overview of ACAR conductor structure, performance parameters, selection methodology, and application scenarios in accordance with ASTM B524, IEC 61089, and IEEE 524 international standards.
1. ACAR Conductor Overview
1.1 What is ACAR?
ACAR (Aluminum Conductor Alloy Reinforced) is a type of bare overhead conductor with the following structural characteristics:
- Reinforcing Core: 6201-T81 high-strength aluminum alloy wires providing mechanical strength support
- Conductive Layer: 1350-H19 (EC grade) electrical conductor aluminum wires stranded concentrically, ensuring excellent conductivity
ACAR's typical structure is denoted by codes such as 18/1 (18 aluminum wires + 1 aluminum alloy core wire), 24/7, 30/7, etc., where the numbers represent the count of outer aluminum wires and inner alloy core wires respectively.
1.2 ACAR vs ACSR vs AAAC
| Property | ACAR | ACSR (Steel Reinforced) | AAAC (All Aluminum Alloy Conductor) |
|---|---|---|---|
| Core Material | 6201-T81 Aluminum Alloy | Galvanized Steel / Aluminum-Clad Steel | No separate core (homogeneous alloy) |
| Conductive Layer Material | 1350-H19 Aluminum | 1350-H19 Aluminum | 6201-T81 Aluminum Alloy |
| Conductivity | ~53%-56% IACS | ~40%-43% IACS | ~52.5% IACS |
| Strength-to-Weight Ratio | Medium | High | Medium-High |
| Corrosion Resistance | Excellent (all-aluminum) | Moderate (steel needs galvanizing) | Excellent |
| Sag Characteristics | Good | Excellent (low thermal expansion) | Good |
| Engineering Cost | Medium-High | Medium-Low | Medium |
2. Technical Standards & Specifications
2.1 Applicable Standards
ACAR conductors are manufactured and tested in accordance with the following international and regional standards:
| Standard | Title | Scope |
|---|---|---|
| ASTM B524 | Standard Specification for Concentric-Lay-Stranded Aluminum Conductors, Aluminum-Alloy Reinforced | ACAR construction, stranding & performance |
| IEC 61089 | Round Wire Concentric Lay Overhead Electrical Stranded Conductors | International overhead conductor standard |
| ASTM B230 | Specification for Aluminum 1350-H19 Wire | EC grade aluminum wire requirements |
| ASTM B398 | Specification for Aluminum-Alloy 6201-T81 Wire | 6201-T81 alloy wire requirements |
| BS EN 50182 | Conductors for Overhead Lines — Round Wire Concentric Lay Stranded Conductors | European standard |
| IEEE 524 | Guide for the Installation of Overhead Transmission Line Conductors | Installation guidelines |
2.2 Typical Specifications
The following table shows typical ACAR conductor specifications supplied by SiTong Cable (based on ASTM B524):
| Code | Al/Alloy Wires | Cross Section (mm²) | Diameter (mm) | Weight (kg/km) | Rated Breaking Strength (kN) | DC Resistance (Ω/km @ 20°C) |
|---|---|---|---|---|---|---|
| ACAR 18/1 AWG #4 | 18/1 | 21.15 | 6.24 | 58.3 | 8.45 | 1.350 |
| ACAR 18/1 AWG #2 | 18/1 | 33.62 | 7.86 | 92.6 | 13.28 | 0.849 |
| ACAR 24/7 85 mm² | 24/7 | 85.02 | 12.50 | 234.5 | 32.80 | 0.345 |
| ACAR 30/7 125 mm² | 30/7 | 125.10 | 15.16 | 345.0 | 47.22 | 0.233 |
| ACAR 30/7 150 mm² | 30/7 | 150.02 | 16.60 | 413.7 | 56.60 | 0.194 |
| ACAR 30/7 200 mm² | 30/7 | 200.03 | 19.17 | 551.6 | 75.48 | 0.145 |
| ACAR 30/7 250 mm² | 30/7 | 250.04 | 21.43 | 689.5 | 94.35 | 0.116 |
| ACAR 30/7 300 mm² | 30/7 | 300.05 | 23.48 | 827.4 | 113.22 | 0.097 |
| ACAR 30/7 400 mm² | 30/7 | 400.06 | 27.12 | 1103.2 | 150.96 | 0.072 |
| ACAR 54/7 500 mm² | 54/7 | 500.08 | 30.32 | 1379.0 | 188.70 | 0.058 |
Note: Specific specifications and performance parameters are subject to factory test reports. Custom non-standard specifications are available upon request.
2.3 Material Properties
| Parameter | 1350-H19 Aluminum (EC Grade) | 6201-T81 Aluminum Alloy |
|---|---|---|
| Conductivity | ≥ 63% IACS | ≥ 52.5% IACS |
| Minimum Tensile Strength | 200 MPa | 325 MPa |
| Resistivity at 20°C | ≤ 0.028264 Ω·mm²/m | ≤ 0.03282 Ω·mm²/m |
| Modulus of Elasticity | 69 GPa | 62 GPa |
| Coefficient of Linear Expansion | 23.0 × 10⁻⁶ /°C | 23.0 × 10⁻⁶ /°C |
| Density | 2.703 g/cm³ | 2.703 g/cm³ |
3. ACAR Construction Design & Selection
3.1 Construction Code Explanation
The ACAR code A/B denotes: A = number of outer 1350 aluminum wires, B = number of inner 6201 alloy core wires.
Common constructions include:
| Code | Description | Al/Alloy Ratio | Typical Application |
|---|---|---|---|
| 18/1 | 1 alloy core + 18 Al wires | 95% / 5% | Small-section distribution lines |
| 24/7 | 7 alloy cores + 24 Al wires | 77% / 23% | Medium-section transmission lines |
| 30/7 | 7 alloy cores + 30 Al wires | 81% / 19% | Large-section backbone transmission |
| 30/19 | 19 alloy cores + 30 Al wires | 61% / 39% | Heavy ice zone, long-span lines |
| 54/7 | 7 alloy cores + 54 Al wires | 89% / 11% | EHV transmission |
| 54/19 | 19 alloy cores + 54 Al wires | 74% / 26% | Extra-large section (400 mm²+) |
Selection Principles: - Higher alloy core ratio → higher mechanical strength → suitable for long spans, heavy ice zones - Higher aluminum wire ratio → higher conductivity → suitable for high-capacity transmission
3.2 Current-Carrying Capacity (Based on IEEE 738)
According to the IEEE 738 steady-state thermal balance model, ACAR conductor ampacity is affected by:
- Maximum Continuous Operating Temperature: Typically 75°C ~ 100°C (special heat-resistant types up to 150°C)
- Environmental Conditions: Wind speed 0.6 m/s (typical), ambient temperature 40°C, solar radiation 1000 W/m²
- Resistance Temperature Coefficient: 1350 Aluminum 0.00403 /°C; 6201 Alloy 0.00347 /°C
Sample Ampacity (ACAR 30/7 200 mm²): | Operating Temperature | Ampacity (A) | |---------------------|-------------| | 75°C | ≈ 520 A | | 85°C | ≈ 600 A | | 90°C | ≈ 635 A | | 100°C | ≈ 700 A |
Note: Values above are reference figures under standard conditions. Actual ampacity should be calculated based on specific project parameters.
3.3 Sag Characteristics Comparison
ACAR's thermal expansion coefficient is close to ACSR, but due to its all-aluminum structure (no steel core), sag performance at high temperatures falls between ACSR and AAAC:
| Conductor Type | Thermal Expansion Coeff. (×10⁻⁶/°C) | High-Temperature Sag |
|---|---|---|
| ACSR (steel core) | 17.8 ~ 21.2 | Best (low steel expansion) |
| ACAR | 23.0 | Good |
| AAAC | 23.0 | Good (same as ACAR) |
| ACSS (annealed Al/steel core) | 17.8 ~ 21.2 | Excellent (self-damping type even better) |
4. Key Application Scenarios
4.1 Long-Distance Transmission Lines
ACAR is widely used in 110kV ~ 500kV overhead transmission lines due to its excellent strength-to-weight ratio. Compared to ACSR, ACAR's all-aluminum structure eliminates steel core corrosion risk, making it ideal for coastal salt-spray environments and industrial pollution zones.
4.2 Long-Span Crossings
For river and valley crossings with spans exceeding 800m, ACAR constructions with high alloy core ratios (e.g., 30/19) provide sufficient mechanical strength while maintaining good conductivity.
4.3 Heavy Ice Zone Lines
In regions with significant ice loading (southern China, high-altitude mountainous areas), ACAR's high-strength alloy core offers additional tensile margin. Constructions with high alloy core ratios such as 30/19 or 54/19 are recommended.
4.4 Line Uprating (Reconductoring)
Replacing existing ACSR with ACAR on existing towers without structural modification can increase ampacity by 10%~20% while reducing tower loads. The lighter weight of the all-aluminum structure is particularly advantageous for towers with limited load margin.
4.5 Coastal & Corrosive Environments
The all-aluminum construction (no steel core) fundamentally eliminates galvanic corrosion risk. ACAR offers significant advantages over ACSR in coastal areas, chemical plants, and other corrosive environments.
5. ACAR vs Other Conductors
5.1 ACAR vs ACSR
| Comparison | ACSR | ACAR | Verdict |
|---|---|---|---|
| Current capacity (same section) | Baseline | +10%~15% | ACAR wins |
| Tensile strength | High (steel core) | Medium-High | ACSR wins |
| Corrosion resistance | Moderate (galv. steel needs maintenance) | Excellent | ACAR wins decisively |
| Weight | Heavier | 10%~15% lighter | ACAR wins |
| Sag performance | Excellent | Good | ACSR wins |
| Jointing technique | Steel-Al transition needed | All-aluminum unified | ACAR wins |
| Service life | 30-40 years (shorter in corrosive) | 40-50 years | ACAR wins |
5.2 ACAR vs AAAC
| Comparison | AAAC | ACAR | Verdict |
|---|---|---|---|
| Conductivity | 52.5% IACS | 53%-56% IACS | ACAR slightly better |
| Tensile strength | Medium-High | Medium (adjustable via alloy ratio) | AAAC slightly better |
| Manufacturing cost | Medium | Medium (slightly lower than AAAC) | ACAR more economical |
| Strength tunability | Fixed (homogeneous) | Adjustable (Al/alloy ratio) | ACAR more flexible |
| Bending fatigue | Good | Good | Comparable |
Compare more overhead conductors: See our ACSR vs AAAC vs ACSS Comparison and AAC vs ACSR Technical Comparison.
6. Installation & Maintenance
6.1 Installation Guidelines
- Stringing Tension: ACAR's modulus of elasticity (E ≈ 62-69 GPa) is slightly lower than ACSR. Stringing tension should be calculated based on actual span length to avoid over-tensioning that could fatigue the alloy core
- Bending Radius: Minimum bending radius during installation and pulling should not be less than 20 times the conductor outer diameter
- Hardware Selection: Aluminum alloy compression fittings and dead-end clamps are recommended. Avoid steel fittings in direct contact with aluminum to prevent galvanic corrosion
- Terminal Connectors: ACAR's all-aluminum structure eliminates the need for steel-aluminum transition joints, simplifying installation
6.2 Operational Maintenance
- Infrared Thermography: Periodically check for temperature anomalies at joints and dead-end clamps
- Vibration Monitoring: Install vibration dampers or spiral vibration dampers on long-span sections
- Corrosion Inspection: Although the all-aluminum structure has excellent corrosion resistance, sample inspections every 3-5 years are recommended in coastal areas
- Sag Re-measurement: Perform initial sag re-measurement after 1 year of operation to verify conductor creep stabilization
7. Frequently Asked Questions (FAQ)
Q1: Can ACAR be directly replaced on existing ACSR lines?
Yes, but tower load verification is required. ACAR is approximately 10%~15% lighter than ACSR of the same cross-section, which typically reduces tower loads. However, ACAR's sag characteristics differ slightly, so ground clearance must be verified. We recommend completing sag verification over at least 3 spans before proceeding with batch replacement.
Q2: What is the maximum continuous operating temperature of ACAR?
Standard ACAR has a maximum continuous operating temperature of 90°C, with short-term emergency operation up to 100°C. Heat-resistant alloy versions (modified 6201-T81) can reach 150°C. Refer to the manufacturer's technical manual for specific ratings.
Q3: Is ACAR suitable for OPGW companion lines?
Yes. ACAR's all-aluminum structure matches well with OPGW's aluminum tube/aluminum alloy tube, with consistent thermal expansion coefficients that reduce hardware fatigue from differential thermal expansion. See our OPGW Technical Overview for details.
Q4: What is ACAR's service life in marine environments?
In coastal salt-spray environments (corrosivity class C1 ~ C5), ACAR's all-aluminum construction eliminates steel core corrosion, achieving a service life of 40+ years — significantly outperforming ACSR (approximately 20-30 years under the same conditions).
Q5: Is ACAR suitable for compact transmission lines?
Yes. ACAR's smooth surface and good sag characteristics help reduce phase-to-phase spacing, making it suitable for compact tower designs. Contact the SiTong Cable technical team for customized structural optimization recommendations.
Q6: Are ACAR and ACSR hardware compatible?
Most ACSR hardware can be used with ACAR, but fittings in contact with aluminum wires (compression connectors, dead-end clamps) should be made of aluminum alloy or aluminum to avoid dissimilar metal contact. All-aluminum hardware is recommended for best results.
8. Why Choose SiTong Cable?
- ✅ Full ASTM/IEC Standard Production: ACAR conductors manufactured to ASTM B524 and IEC 61089
- ✅ Custom Construction Design: Supports 18/1 ~ 54/19 constructions and non-standard specifications
- ✅ Rigorous Quality Testing: 100% mechanical property and conductivity testing before shipment
- ✅ Global Export Experience: Products exported to 30+ countries across Southeast Asia, South America, Africa, and the Middle East
- ✅ Technical Support: Sag calculation, ampacity analysis, and on-site installation guidance
Related Product Pages: HTLS Conductor Series | AAC All-Aluminum Conductor | AAAC All Aluminum Alloy Conductor | ACSR Steel Reinforced Conductor | Overline Fittings
Technical data compiled in accordance with ASTM B524-20, IEC 61089:2024, and IEEE 738-2023. Specifications are for reference only. Please refer to formal technical documentation provided by the manufacturer for final engineering design.
SiTong Cable — Your Professional Overhead Conductor Partner | Contact: sales@sitongcable.com
